Wear gloves, eye protection, and a mask
Sweep or rinse the area to remove loose dirt
Test a small hidden spot first
Apply a concrete-safe paint remover or graffiti remover
Let it sit for the recommended time
Scrub with a stiff-bristle brush
Rinse with water
Repeat as needed
Use a pressure washer if the cement can handle it
For stubborn spots, apply acetone or mineral spirits sparingly
Scrub again and rinse thoroughly
Use a poultice or absorbent cleaner for deep stains
Seal the concrete after cleaning if desired